Cheap But Imperfect Can Geoengineering Slow Climate Change?

Canadian environmental scientist David Keith wants to change the world's climate by creating a type of sun filter in the sky to halt global warming. In an interview, he argues the technology is effective and inexpensive, but critics liken it to a nuclear bomb.

The 1991 explosion of the Mount Pinatubo volcano in the Philippines. "Aerosoles in the stratosphere reduce the rate of climate change," says David Keith.

The 1991 explosion of the Mount Pinatubo volcano in the Philippines. "Aerosoles in the stratosphere reduce the rate of climate change," says David Keith.

Interview by

While delegates meeting in Warsaw at the United Nations climate talks push for targets for reducing greenhouse gases, a small splinter group of scientists is promoting an entirely different approach to fighting climate change: They want to artficially manipulate the planet's climate to help stop global warming.

The name most commonly associated with this "geoengineering" is David Keith, a 50-year-old environmental scientist from Canada. Keith is arguably the best-known advocate of geoengineering. When he first devoted himself to the idea more than 20 years ago, it was considered dangerous nonsense. It enraged climate activists, and even Keith received death threats on his answering machine.

Since then, the concept of geoengineering has increasingly won over supporters, and the Intergovernmental Panel on Climate Change (IPCC) even grappled with the issue in its most recent report.

Keith runs a company called Carbon Engineering in Calgary, which is developing technology to capture carbon dioxide directly from the atmosphere. He currently travels back and forth between Calgary and Cambridge, Massachusetts, where he is a professor of applied physics and public policy at Harvard University.

He recently sat down with SPIEGEL for an interview about his work.

SPIEGEL: Professor Keith, are you a climate fixer?

Keith: That's what they said in the New Yorker, right? People have called me all sorts of things. But I wouldn't say that. I'm a professional whose work is on climate technology, on so-called geoengineering.

SPIEGEL: How would you describe the goal of climate engineers?

Keith: Geoengineering is the deliberate attempt to alter the climate on a global scale.

SPIEGEL: That's quite a bold claim. The New Yorker quotes you saying that you could easily imagine how the tools of climate engineering could spur "a chain of events that would extinguish life on earth."

Keith: … and a lot of my colleagues were unhappy I said that. What I mean by that is the following: If we use this technology with wisdom and humility, and in combination with big emission cuts, then it will almost certainly be a benefit to the world. But it's our responsibility to ask: What is the worst that could happen? What if the user goes nuts? What if humanity decided to commit some kind of racial suicide?

SPIEGEL: Then, you want to say, geoengineering might be the technology to use? In other words: You are dealing here with the most dangerous technology in the world?

Keith: Well, yes and no. There has been a lot of talk about the analogy to nuclear weapons. And in one way the analogy makes sense: This technology has a huge amount of leverage, meaning relatively small amounts of material give a huge amount of power. But the big difference is it all moves slowly -- in years, not minutes. This gives us more room to think and proceed carefully.

SPIEGEL: Critics have accused geoengineers of trying to play God …

Keith: … and maybe it's a fair attribution. I don't think I'm playing God, but I do think the phrase captures some of what's going on here: the desire to deliberately alter nature on a global scale.

SPIEGEL: And you share this desire?

Keith: Well, mankind is already changing the planet. Take agriculture, the emission of carbon dioxide, the intervention in the nitrogen cycle.

SPIEGEL: But in all those cases people didn't intend to change the planet.

Keith: You're right, but intention matters -- as we also distinguish between manslaughter and murder. But the intention of myself and my colleagues is actually to reduce mankind's impact on the natural environment, which is very different from the intent to design it to our liking. As long as we just try to slow down the rate of climate change, I wouldn't say that we are playing God.

SPIEGEL: How exactly would you slow down climate change?

Keith: The idea is to make earth a little bit more reflective by putting say, sulfate or sulfuric acid aerosols in the upper atmosphere. This method is cheap, effective, quickly implantable but rather imperfect.

David Keith is a professor of applied physics and public policy at Harvard University.
Keiko Hiromi/ DER SPIEGEL

David Keith is a professor of applied physics and public policy at Harvard University.

SPIEGEL: Why imperfect?

Keith: Because it cannot deal with all problems with CO2 in the atmosphere. For example, it does nothing about ocean acidification.

SPIEGEL: And what do you mean by "cheap?"

Keith: According to my estimate the injection of a dose with an appreciable effect on climate would cost about a $1 billion per year -- which is essentially zero if you compare it to the costs of climate damage, which are expected to be at least a $1 trillion a year by mid-century.

SPIEGEL: A billion dollars! This is, in fact, frighteningly cheap. It means that any billionaire could start to change the climate according to his will?

Keith: True. We have a case here, where low cost is not necessarily good. But I don't consider it to be very credible that an individual would be doing this. A government would be able to prevent him.

SPIEGEL: And what if some small island state that feels threatened by rising sea levels decides to cool down the earth a little bit?

Keith: Even in that case the international community has lots of mechanisms to stop this. My real concern is the big countries, like Indonesia, India or the United States.

SPIEGEL: Whoever injects sulfur into the stratosphere will put heavy risks on health and environment. This doesn't frighten you?

Keith: No doubt there are considerable risks. Eventually the sulfur will settle down into the lower atmosphere. And then there's the ozone loss risk.

SPIEGEL: Ozone damage means more ultraviolet radiation on earth, and this means an increase in skin cancer fatalities. Would you accept fatalities for the sake of climate therapy?

Keith: I don't think the fundamental justification is hard. We routinely introduce technologies which threaten some people. If you build a power plant, you are adding some air pollution, and new air pollution means deaths. And, by the way, the net impact of sulfur aerosols on mortality is by no means sure. They do reduce ozone, but they also increase UV scattering, which reduces UV exposure down on earth.

SPIEGEL: How well do you know whether you can actually achieve your ultimate goal to slow down climate change with these sulfur aerosols?

Keith: Well, we know a lot about that. Aerosols in the stratosphere reduce the rate of climate change. This is what we expect from basic theory; this is what we observe after eruptions of volcanoes like Pinatubo (which erupted in the Philippines in 1991); and this is what we see in every climate model that has ever been tested for the impact of aerosols.

SPIEGEL: Some people seem to be concerned that the Asian monsoon might be severely altered by such an aerosol therapy.

Keith: The Indian monsoon has indeed become a touchstone of this confused debate. The whole argument started with an early paper by Alan Robock, who said that geoengineering could shut down the monsoon and threaten billions of lives. He is right to focus on potential impacts on the poor, but the really bad outcomes only come when models are run with a crazy amount of geoengineering. Most models -- including Alan's own results -- show that modest interventions can significantly reduce climate impacts in the Indian subcontinent. It's as in pharmacology: An overdose of a drug is fatal -- but a small dose can save a life.

Graphic: Scientists would like to slow global warming by reproducing the effects of a volcano.

Graphic: Scientists would like to slow global warming by reproducing the effects of a volcano.

SPIEGEL: When you talk about manipulating the climate, do you mean the regulation of average world temperature as a whole, or will it someday also be possible to tune climate differently in different locations?

Keith: This is delicate question. As an engineer you think, the more control the better. But I think in this case we might be better off if we couldn't turn too many knobs. While I oppose any military use of climate technology, you can be sure of one thing: The more targeted or tailored this technology gets, the more seriously military use will be considered.

SPIEGEL: Is it technically feasible to fine-tune the climate locally?

Keith: Sure it is. I have even published on this, but I wonder how much we should go on in this direction.

SPIEGEL: You won't be able to detain research anyway.

Keith: Not perfectly, but a little bit. Public programs have clearly stated goals. And you have the choice, whether making tailored modifications should be one of those goals.


Discuss this issue with other readers!
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redroseandy 11/21/2013
1. optional
Near-Zero CO2 Plans have not been taken seriously by governments, even though the first one was invented in the 1980s.
paullang 11/21/2013
2. Why not paint mountains and natural snow fields white?
This would mimic the effects of snow with whitewash, It could also be sprayed from planes much as agent orange was during the Vietnam war. It has the benifits of being a passive method, and once done it would last a long time.
psychocat7 11/21/2013
3. climate change solutions
Before the Canadians can solve the problem, don't they have to admit there is one? And like Occam's Razor, the simplest solutions will be the answer. But will we run out of oil, gas, and coal before it is too late?
spon-facebook-10000061525 11/22/2013
4. optional
Why so much time, energy and resources are put into this climate change issue? The world has much greater problems, like a secure food suppy, bringing billions out of poverty, overpopulation, and
RodMartinJr 11/04/2015
5. Climate Change Hoax
I love science. I'm not wild about when science is stirred in with lots of political wrangling. Climate has changed for nearly 4.5 billion years, yet the UN and others have corrupted the term to refer only to a very modern, so-called problem. I say, "so-called," because we're currently in an ICE AGE! Instead of NASA referring to global warming as "Earth's fever," they should refer to it as "Earth's thaw." Am I the only one who thinks it's a bit loony to cool down the planet in the midst of the current Ice Age? Has Big Money so corrupted science that we're now in a New Dark Age without anyone noticing? Yeah, go ahead. Cool down the planet. End the Holocene early (only it's not early, because it's already 600 years overdue). Consequences of ushering in the next glacial period of the current Ice Age: * 90,000 years of frozen climate * Scarce rain fall * Failed crops * Massive starvation (somewhere in the 7 Billion range). This elephant seems pretty big, but everyone seems to be ignoring it as if they didn't care. But that sounds like any typical psychopath; they don't care about right and wrong. With a few $Trillion, they can do anything they want. Tax the little people to push them toward oblivion while cooling down the planet. I wonder how big their food stores are. And please, if you think of making some wise crack about "conspiracies," there are at least 489 new conspiracies starting every second, somewhere on Earth, day-in and day-out, all year long and every year. Conspiracies are Dirt Ordinary, because people are selfish or self-concerned. Wake up and smell the ice before you're buried in it.
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